Selective inhibitors of DNA polymerases, N6-substituted 6-aminopyrimidines and related compounds, will be designed as probes of the structure and function of Bacillus subtilis DNA polymerase III and mammalian DNA polymerase alpha, and as leads in the design of antibacterial and anticancer agents. Synthesis and exploitation of site-directed irreversible inhibitors will be done to label the inhibitor binding sites of DNA polymerases III and alpha, to examine the nature of inhibitor-enzyme-template interaction, to isolate inhibitor binding site peptides, and to determine the relationship between the active sites and inhibitor binding sites of the enzymes. Synthesis of nucleoside, nucleotide and other inhibitor analogs are planned to further probe the inhibitor binding sites of both enzymes, and to generate potent and selective inhibitors of bacterial and mammalian cell division as potential chemotherapeutic agents. The mechanism of inhibition of AMV reverse transcriptase by 5-benzyl-6-amino-uracils will be explored through structure activity relationships of analogs, and through spectroscopic and enzymological experiments examining interaction of inhibitor, enzyme and templates.